Embodiments of the invention relate generally to the field of wind energy, and more particularly to the use of augmenters to enhance air velocity into the blade or impact impeller area and augmenter with walls, such as flexible walls.
With considerable attention toward renewable energy, the efficient use of wind power and the capturing of increased energy from the winds has received much consideration. One attempt to harness increased wind energy power is disclosed in U.S. Pat. No. 4,070,131 wherein ambient wind is admitted into a vertical structure producing a vortex flow and corresponding low pressure area for enhancing air flow across a wind turbine.
U.S. Pat. No. 4,031,405 discloses a horizontal turbine with a wind enhancement structure which adjusts to the direction of wind for optimizing the wind velocity.
Other methods have been proposed for directing the wind and increasing its effects against a turbine blade or impact impeller.
Wind turbines utilize a rotor for converting the energy of the air stream into rotary mechanical power as a power conversion device from the wind. Wind machines can take advantage of a free and inexhaustible power source of mechanical power for various purposes including driving an electrical generator. In generating large amounts of power, conventional turbines had large rotors in order to generate a sufficient amount of energy in order to make it worthwhile for having a generator in order to produce electricity. Unfortunately, the large rotors are expensive because the stress on the rotors increases dramatically as the diameter increases. Conventional turbines had to increase the diameter of the blades in order to capture more energy generated by the moving air impacting the blades. This increase in the diameter of blades for producing substantial power can increase the cost of other items in the turbine other than the blades. Large blades which have not been properly produced can create structural stress and fatigue problems for the gearbox, tower, and the system that turns the generator toward the optimal wind direction.
In the past, wind turbines were supported by a single tower and guy wires in many cases leading to many vibration and frequency related problems. The blades of vertical axis turbines were large and could be limited in the design and the materials used. For example aluminum extrusion and fiberglass pultrusion were used in the two most serious commercial applications of vertical axis turbines. Due to the large size of the fiberglass blades, the strength was limited in order to bend the blade at the place of installation. The aluminum blades could not form a true troposkein shape. The blades had to be made of significant length and the available extrusion equipment is not available. The patents of both serious commercial prior applications of vertical axis technology are described in “Vertical Axis Wind Turbine” U.S. Pat. No. 4,449,053 and “Vertical Axis Wind Turbine with Pultruded Blades” in U.S. Pat. No. 5,499,904. However, the fatigue factor in blades using those materials suffered from structural stress caused by cyclical loads on vertical blades. The lift forces push the blades back and forth as they rotate. The more popular horizontal wind turbines are not subject to this cyclical stress occurring many thousand of times per day. The construction and installation was complex and costly.
The vertical blades in prior technology could not place the rotor high enough above the ground in order to a turbulence leading to long term structural problems.
In other prior technology, the swept area of the turbine had an aspect ratio of less than four due to construction limitations. The aspect ratio, the swept area height to diameter, is preferred to be high for better efficiency. This occurs when a tall and thin rotor maintains a large swept area and a high RPM. As a result, the moment of inertia is reduced and less energy is spent on its own motion.
In prior blade technology, two or more blades per shaft section, were used in order to achieve proper blade balance. The designing of one blade per shaft section was expensive and had imbalance problem in past turbines there were numerous attempts toward developing a horizontal one bladed turbine.